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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: ADA task
Date: 1996/09/20
Message-ID: <Dy0AH1.BM@world.std.com>#1/1
X-Deja-AN: 184065916
references: <96091716303787@psavax.pwfl.com> <324159A2.6220@watson.ibm.com>
organization: The World Public Access UNIX, Brookline, MA
newsgroups: comp.lang.ada
Date: 1996-09-20T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <324159A2.6220@watson.ibm.com>,
Norman H. Cohen <ncohen@watson.ibm.com> wrote:
>The Ada-95 Real-Time Annex defines certain "metrics" of real-time
>performance, including metrics of the performance of both kinds of delay
>statement.  (See RM Section D.9.)  The Annex requires implementations
>claiming conformance to the Annex to document their performance with
>respect to these metrics as well as with respect to several
>nonquantitative aspects of real-time performance.

Yeah, but let's not get carried away with this.  Ada doesn't define
performance, in general, and neither does any other language I know of.
How long does "X := Y;" take, when X and Y are of type Integer?  The RM
doesn't say.  So why are we so worried about the fact that delay
statments might take too long?  Suppose the Ada compiler makes "X := Y;"
take 1 second.  Is that acceptable?  Well, no, but it has nothing to do
with the RM.  Likewise, suppose a task's delay expires, and the run-time
system doesn't notice that fact for 1 second.  Is that acceptable?  No,
but it's not the fault of the language.  It's the fault of the Ada
implementation, or maybe the OS it's running on top of.  (I'm appalled
that certain OS's can't measure time more accurately than 1/18 second!)

- Bob